U.S. Pat. Nos. 6,536,657 and 6,729,534 and U.S. Patent Publication No. 2005-0029337, which disclosures are incorporated herein in their entireties by this reference, disclose a beverage container having a film adhered to the interior thereof. When the container is filled with a hot liquid, the film will shrink. Upon shrinking, the film moves away from the interior of the container to create a pocket of air. This air pocket results in the container having insulating characteristics. In these referenced patents and application, an insulating band is instantaneously activated (that is, the film shrinks) by contact with hot liquid. The insulated cups formed by the methods and materials set out in the referenced patents were found to provide excellent insulation properties when used for serving hot beverages, such as coffee, tea etc. However, in use, when the film began to shrink, a partial vacuum was formed and the film could not fully activate to provide maximum insulation effect.
Other types of insulating cups incorporating a plastic interliner are known. For example, U.S. Pat. No. 3,737,093, which disclosure is incorporated herein in its entirety by this reference, discloses a plastic container situated within a paper container to create an air space for thermal insulation. U.S. Pat. No. 4,435,344, which disclosure is also incorporated in its entirety by this reference, discloses a container made from foam polyethylene-coated paperboard which has insulating properties. More recently, U.S. Pat. No. 6,852,381, which disclosure is incorporated herein in its entirety by this reference, describes an insulated beverage container comprising (in order from the outermost surface to the inside of the container): a paperboard outer shell, a foam layer laminated to the inner surface of the paperboard shell and a film adhered to the foam surface. In use, it appears that the film would be in contact with the beverage in the container to pull wrinkles out of the inner container surface.
While the above references disclose a number of different configurations for insulated beverage containers, there remains a need in the art for an insulated beverage container that provides suitable insulation properties for use with hot beverages or other hot materials. The present invention meets such a need.